An anti-fuse memory having a configuration as disclosed in U.S. Pat. No. 6,667,902 (Patent Literature 1) is a known example of a conventional anti-fuse memory to which data can be programmed only once by breaking an insulating film. The anti-fuse memory disclosed in Patent Literature 1 has a two-transistor configuration including a switch transistor and a memory capacitor arranged side by side on a well.
In the switch transistor included in the transistor configuration, a switch gate electrode is disposed on the well through a switch gate insulating film and connected with a word line, and one of diffusion regions formed on the surface of the well is connected with a bit line. In the memory capacitor in a pair with the switch transistor, a memory gate electrode is disposed on the well through a memory gate insulating film and connected with a programming word line different from the word line connected with the switch gate electrode.
At data programming operation, in the memory capacitor, dielectric breakdown occurs to the memory gate insulating film due to a voltage difference between a breakdown word voltage applied from the programming word line to the memory gate electrode and a dielectric breakdown bit voltage applied to the bit line of the switch transistor. Accordingly, the memory gate electrode, which has been insulated from the well, is electrically connected with the surface of the well, in other words, a region in which a memory channel is formed, due to the dielectric breakdown of the memory gate insulating film.
At data reading operation, when breakdown has occurred to the memory gate insulating film and voltage is applied to a programming word line connected with a bit line to be read, the voltage applied to the programming word line is applied to the other diffusion region of the switch transistor through the memory channel. The switch transistor is turned on due to voltages applied from the word line connected with the switch gate electrode and the bit line connected with the diffusion region. Accordingly, the state of electrical connection between the memory gate electrode of the corresponding memory capacitor and the memory channel can be determined based on change in the voltage applied to the bit line to determine whether data is programmed.